chore(frontend): refactor navigation and DI setup, remove unused shared module

- Replaced `initKoin` with `startKoin` for DI initialization consistency across platforms.
- Introduced `StateNavigationPort` with `StateFlow` to streamline navigation state management.
- Migrated `AppScreen` to sealed class with route mapping for better navigation handling.
- Deleted unused `frontend/shared` module and removed related dependencies from build files.
- Cleaned up legacy navigation and Redux-related code, aligning with MVVM architecture.

frontend/shells/meldestelle-portal/src/jvmMain/kotlin/main.kt

@@ -2,7 +2,6 @@ import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
 import androidx.compose.ui.window.WindowState
 import androidx.compose.ui.unit.dp
-import at.mocode.shared.di.initKoin
 import at.mocode.frontend.core.network.networkModule
 import at.mocode.frontend.core.auth.di.authModule
 import at.mocode.frontend.core.sync.di.syncModule
@@ -12,6 +11,7 @@ import at.mocode.frontend.core.localdb.DatabaseProvider
 import at.mocode.frontend.core.localdb.localDbModule
 import navigation.navigationModule
 import kotlinx.coroutines.runBlocking
+import org.koin.core.context.startKoin
 import org.koin.core.context.loadKoinModules
 import org.koin.dsl.module
 
@@ -19,7 +19,7 @@ fun main() = application {
   // Initialize DI (Koin) with shared modules + network module
   try {
     // Updated: Only load the consolidated pingFeatureModule from at.mocode.ping.feature.di
-    initKoin { modules(networkModule, syncModule, pingFeatureModule, authModule, navigationModule, localDbModule) }
+    startKoin { modules(networkModule, syncModule, pingFeatureModule, authModule, navigationModule, localDbModule) }
     println("[DesktopApp] Koin initialized with networkModule + authModule + navigationModule + pingFeatureModule + localDbModule")
   } catch (e: Exception) {
     println("[DesktopApp] Koin initialization warning: ${e.message}")